Strange, large star light the same size as Jupiter that moved gracefully and slowly disappeared into very small red light

I was out gazing at Jupiter when in my periphery I noticed another star-like object the same size as Jupiter which shouldn't have been there (abeam and to the left of Jupiter). The object appeared to be slowly moving and was completely silent, and then slowly became smaller and smaller until the white light dimmed to a very small red light and then fizzled out and disappeared. I have never seen anything like it. I observed it for around 45 seconds until it then became smaller and smaller , turned into a very small, difficult to see, red light and eventually disappeared. That process took about 15 seconds.